In the last episode (Jan 23), Mikhail Teterin said:
> =FreeBSD is clearly not capable of hard real-time. If I
> =remember correctly, neither are any of the operating systems from
> =which you quoted man pages. That makes *all* of those man pages
> =inaccurate.
>
> In other words, we found a flow in the most (all?) Unix implementations?
> Including FreeBSD. Alright.
If you want to call it a flaw, then yes. The kernel always has
priority over user processes. If an ethernet packet comes in, a
character is received over a serial port, or a disk wants to return a
block of data requested by the system, your user process *will* stop
and the kernel will processes the interrupt. If that interrupt takes a
while, a select() or poll() may very well return later than the timeout
specified. Apart from writing your own kernel module, blocking all
interrupts, and buzz-looping on a timer variable, there's not much you
can do about it under Unix. And I'll not even mention what happens to
this when you start swapping.
--
Dan Nelson
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